This invention relates to the trajectory of a spacecraft reentering the atmosphere.
Controlling acceleration of a spacecraft reentering the atmosphere is not, in itself, a new concept. The usual reasons for controlling acceleration during reentry are to: (1) reduce g-loads on the payloads or humans in the vehicle, or (2) reduce the aeroheating (heating due to compression and friction from the air) experienced by the spacecraft. Historically, from Mercury through Shuttle, the only methods employed to control acceleration have been: (a) using rotations to control the vehicle""s angle of attack, or (b) using rotations to control the vehicle""s lift-to-drag ratio. The term xe2x80x9crotationsxe2x80x9d refers to controlling the direction in which the vehicle is facing, commonly called pitch yaw and roll, using relatively small rocket thrusters (attitude control system), shifting center of gravity, wing ailerons, body flaps, or combinations of these. The term xe2x80x9crelatively smallxe2x80x9d means large enough to rotate the vehicle, but too small to provide significant translational movement (i.e., also referenced as longitudinal movement). Some small translational acceleration usually accompanies rotations, but it is usually orders of magnitude smaller than the vehicle""s translational speed. The only translational rocket burns they have employed have been: (i) retro-rocket de-orbit burns. executed in space (above 100 km altitude), well above the atmosphere, to change their path to intersect the atmosphere, or (ii) landing deceleration, executed just above the ground, such as performed by the Apollo Lunar Lander, Mars Rover, or DC-X.
A need exists for trajectories capable of providing reentry of a spacecraft into the atmosphere under conditions designed to accommodate the special needs and/or interests of adventure travelers.